98%-ish carnivore since Sep 2018.
Pros - pretty much everything
Cons - wife, and almost everyone else, thinks I'm crazy
More specifics:
Pros
I struggled with weight almost all my life. I used to have to work really really hard to try and get semi lean. Now (at 45), I"m way leaner than ever, and can't seem to get fat.
No worries about portion control, or ever being hungry.
Strength, and especially strength to weight is better than ever (30+ hanging pull ups, 2.5x bodyweight deadlifts, etc)
Food cravings are almost entirely gone. Chocolate still tastes good, but only a little bit will do, and I don't have to have it. Or have to have anything really. Red meat satisfies.
Very stable energy levels throughout the day.
I fall asleep quickly.
No more aches/pains. Seem to heal like a much much younger man.
Can go 24 hrs between meals. Most days do 14-16 hours fasted.
Skin is better than ever.
I rarely get sick anymore.
Digestion is almost perfect, also no gas or bloating...ever.
My teeth don't make plaque....brushing teeth is optional
Over time, eating becomes intuitive. Just fill up on fatty meat (to taste), salt to taste, and drink water to thirst. Almost like a wild animal in its natural environment.
Its a great tool to figure out how your body reacts to different foods (after giving a sufficient of being relatively strict)
You can gain great metabolic flexibility in the end, ability to burn whatever for fuel (including some carbs)
I don't bonk after hours and hours of exercise. May get tired eventually, but there's no more crash.
It's stupid simple to eat and shop. You don't need all that variety and 47 different items at the grocery store.
Cons
There is an adaptation period. Initially expect some fatigue until you get decently fat adapted. If you're already fat adapted (keto), it's not so bad
May take awhile to get salts/electrolites/water and fat/lean figured out. In the end, taste should be a good guide.
You're probably going to get the runs for awhile. Might get constipation too, but some of that may be just understanding that there won't be nearly as much waste to poop out....food gets absorbed and used.
It's socially awkward, at least if you're being strict.
You will likely find yourself especially sensitive to non-animal foods after being strict carnivore for a time. This isn't all bad though....some of it may be that you get used to feeling really good (finally!), then it's a shock when you eat something plant based. However, if you start reintroducing foods after some months, you may find you're less sensitive (like less digestive distress), almost like you've given your gut time to heal.
2 years into this, I still eat 98-100% carnivore most of the time. And if I need to eat some carbs (like that's what available on a hunting/camping trip or traveling), then no biggie. Once you get over the hump (like there's no more cravings), then life gets easy. I now eat just enough carbs, just often enough, to know that I still can. So I've got all the benefits of carnivore, but I'm also gained tremendous metabolic flexibility. I could eat 200 grams of carbs on a big exertion day and its not a big deal (and its kinda like rocket fuel). Or I could eat 0 carbs, and its like burning mostly diesel.
Zach Bitter and Shawn Baker on the human performance outliers podcast are great resources for this stuff. Zach is an ultramarathoner, and mostly carnivore, but he strategically uses a little bit of carbs....probably a smart way to go. Baker is more strength/high intensity and has been strict carnivore for like 4-5 years now.
Hope that helps
James